Noble gases and mineralogy of primary igneous materials of the Yamato-793605 shergottite

Mineralogical and petrologic study on the Y-793605 lherzolitic shergottite using an optical microscope and an electron microprobe shows that this meteorite is a primary cumulate rock with close affinity to ALH77005 (and possibly to LEW88516), and is different from Shergotty. Strong shock effects. 30-50 GPa, are observed as finely fractured texture of pyroxene, maskelynite and brownish color olivine. Noble gas analyses by total melt and stepwise heating were performed on 17.86 and 50.99 mg primary igneous materials from Y-793605,10,respectively. Xe isotopic ratios show weak isotope signature for shergottite, which is different from those of nakhlites, Chassigny and ALH84001. Cosmic-ray exposure ages calculated from cosmogenic ^3He and ^Ne are 5.1-5.8 Ma, which is slightly longer than the ages, 3.3-4.0 Ma, reported for other two lherzolitic shergottites ALH77005 and LEW88516. Multistage exposure to cosmic-rays would be responsible for the difference. Apparent K-Ar age of 1430-1860 Ma is calculated, which is concordant with the young crystallization ages for martian meteorites, though the age is still ambiguous

Noble gases, chemical composition, and cosmic-ray exposure age of the Yamato-74357 lodranite

Cosmic-ray produced ^3He, ^Ne, and ^Ar concentrations and the chemical composition of the Yamato-74357 lodranite have been determined. Concordant concentrations of ^3He and ^Ne have been obtained on both samples (Bern and Misasa). The concentration of cosmogenic ^Ar is twice as high in the Bern as in the Misasa sample. The ^3He, ^Ne and ^Ar data for both samples yield an average cosmic-ray exposure age of 5.8±2.0Ma. This age indicates that Yamato-74357 belongs to the lodranite group, which probably originates from a common break-up event about 5Ma ago. Radiogenic ^4He and ^Ar concentrations in the Bern sample are higher than those in the Misasa sample by more than a factor of two, suggesting that minerals enriched in U, Th and K are enriched in the finer grained fraction. The isotopic compositions of Kr and Xe are identical to those of the terrestrial atmosphere, except for the ^Xe abundance. The small ^Xe excess (^Xe/^Xe=1.15±0.04) is presumably due to the early formation of this meteorite

Brain Training Game Improves Executive Functions and Processing Speed in the Elderly: A Randomized Controlled Trial

The beneficial effects of brain training games are expected to transfer to other cognitive functions, but these beneficial effects are poorly understood. Here we investigate the impact of the brain training game (Brain Age) on cognitive functions in the elderly.Thirty-two elderly volunteers were recruited through an advertisement in the local newspaper and randomly assigned to either of two game groups (Brain Age, Tetris). This study was completed by 14 of the 16 members in the Brain Age group and 14 of the 16 members in the Tetris group. To maximize the benefit of the interventions, all participants were non-gamers who reported playing less than one hour of video games per week over the past 2 years. Participants in both the Brain Age and the Tetris groups played their game for about 15 minutes per day, at least 5 days per week, for 4 weeks. Each group played for a total of about 20 days. Measures of the cognitive functions were conducted before and after training. Measures of the cognitive functions fell into four categories (global cognitive status, executive functions, attention, and processing speed). Results showed that the effects of the brain training game were transferred to executive functions and to processing speed. However, the brain training game showed no transfer effect on any global cognitive status nor attention.Our results showed that playing Brain Age for 4 weeks could lead to improve cognitive functions (executive functions and processing speed) in the elderly. This result indicated that there is a possibility which the elderly could improve executive functions and processing speed in short term training. The results need replication in large samples. Long-term effects and relevance for every-day functioning remain uncertain as yet.UMIN Clinical Trial Registry 000002825

Noble gas and oxygen isotope studies of aubrites: A clue to origin and histories

Noble gas measurements were performed for nine aubrites: Bishopville, Cumberland Falls, Mayo Belwa, Mount Egerton, Norton County, Peña Blanca Spring, Shallowater, ALHA 78113 and LAP 02233. These data clarify the origins and histories, particularly cosmic-ray exposure and regolith histories, of the aubrites and their parent body(ies). Accurate cosmic-ray exposure ages were obtained using the 81Kr–Kr method for three meteorites: 52 ± 3, 49 ± 10 and 117 ± 14 Ma for Bishopville, Cumberland Falls and Mayo Belwa, respectively. Mayo Belwa shows the longest cosmic-ray exposure age determined by the 81Kr–Kr method so far, close to the age of 121 Ma for Norton County. These are the longest ages among stony meteorites. Distribution of cosmic-ray exposure ages of aubrites implies 4–9 break-up events (except anomalous aubrites) on the parent body. Six aubrites show “exposure at the surface” on their parent body(ies): (i) neutron capture 36Ar, 80Kr, 82Kr and/or 128Xe probably produced on the respective parent body (Bishopville, Cumberland Falls, Mayo Belwa, Peña Blanca Spring, Shallowater and ALHA 78113); and/or (ii) chondritic trapped noble gases, which were likely released from chondritic inclusions preserved in the aubrite hosts (Cumberland Falls, Peña Blanca Spring and ALHA 78113). The concentrations of 128Xe from neutron capture on 127I vary among four measured specimens of Cumberland Falls (0.5–76 × 10−14 cm3STP/g), but are correlated with those of radiogenic 129Xe, implying that the concentrations of (128Xe)n and (129Xe)rad reflect variable abundances of iodine among specimens. The ratios of (128Xe)n/(129Xe)rad obtained in this work are different for Mayo Belwa (0.045), Cumberland Falls (0.015) and Shallowater (0.001), meaning that neutron fluences, radiogenic 129Xe retention ages, or both, are different among these aubrites. Shallowater contains abundant trapped Ar, Kr and Xe (2.2 × 10−7, 9.4 × 10−10 and 2.8 × 10−10 cm3STP/g, respectively) as reported previously (Busemann and Eugster, 2002). Isotopic compositions of Kr and Xe in Shallowater are consistent with those of Q (a primordial noble gas component trapped in chondrites). The Ar/Kr/Xe compositions are somewhat fractionated from Q, favoring lighter elements. Because of the unbrecciated nature of Shallowater, Q-like noble gases are considered to be primordial in origin. Fission Xe is found in Cumberland Falls, Mayo Belwa, Peña Blanca Spring, ALHA 78113 and LAP 02233. The majority of fission Xe is most likely 244Pu-derived, and about 10–20% seems to be 238U-derived at 136Xe. The observed (136Xe)Pu corresponds to 0.019–0.16 ppb of 244Pu, from which the 244Pu/U ratios are calculated as 0.002–0.009. These ratios resemble those of chondrites and other achondrites like eucrites, suggesting that no thermal resetting of the Pu–Xe system occurred after 4.5 Ga ago. We also determined oxygen isotopic compositions for four aubrites with chondritic noble gases and a new aubrite LAP 02233. In spite of their chondritic noble gas signatures, oxygen with chondritic isotopic compositions was found only in a specimen of Cumberland Falls (Δ17O of 0.3‰). The other four aubrites and the other two measured specimens of Cumberland Falls are concurrent with the typical range for aubrites